In order to support more applications and higher transmission speed, the third generation cellular system is now rapidly and broadly developing. For making the Universal Mobile Telecommunication System (UMTS) of global mobile communication system achieving seamless connection, it will normally employ the compressed mode to handle the inter-system handover to the Global System for Mobile Communication (GSM) or the Wireless Local Area Network (WLAN).
In the compressed mode, it will interrupt the current connection, so as to measure the carrier wave of other systems. For the mobile communication in UMTS, it is first required for measuring the strength of carrier wave of other systems between the transmission intervals; then, the mobile communication user could obtain the control channel message from the measurement system based on the associated strength of carrier wave; after completion of collecting the control channel messages, the handover operation will be formally executed.
In order to achieve higher transmission speed and power-less control between transmission intervals, the system must increase the transmission power for the up-link and the down-link, so as to assure the connection quality, however, reduce the capacity on the contrary. Although the compressed mode could help the inter-system handover, some of the system performance will be affected, which is caused by eliminating the power control during the voltage frame.
For example, the U.S. Pat. No. 6,925,095 B2 has disclosed a handover assessment method. But, it did not have enough remaining time and space for dispatching when dealing with more transmission intervals. Moreover, the U.S. Pat. No. 6,618,365 B1 has disclosed a device and method for reducing the up-link, but it only considered the up-link, but not mentioning the down-link. This is the main reason for power consumption.